My first breath was just...it just seemed impossible that you could actually breathe underwater. I knew in my mind it was possible, but actually experiencing it was such a gulp of joy and I feel it every time I go under the ocean. I love doing it, to be able to feel weightless, to spin on one finger, to do somersaults, to be like a graceful ballerina - even with a huge tank on your back you can do the most extraordinary things.

When I first ventured into the Gulf of Mexico in the 1950s, the sea appeared to be a blue infinity too large, too wild to be harmed by anything that people could do.

By the end of the 20th century, up to 90 percent of the sharks, tuna, swordfish, marlins, groupers, turtles, whales, and many other large creatures that prospered in the Gulf for millions of years had been depleted by overfishing.

People ask: Why should I care about the ocean? Because the ocean is the cornerstone of earth's life support system, it shapes climate and weather. It holds most of life on earth. 97% of earth's water is there. It's the blue heart of the planet - we should take care of our heart. It's what makes life possible for us. We still have a really good chance to make things better than they are. They won't get better unless we take the action and inspire others to do the same thing. No one is without power. Everybody has the capacity to do something.

Why does evolution matter? There is so much about the evolution of life, the development of life on Earth that should rivet the attention of everyone to understand where we've come from and where we might be going. We need to understand the world around us if we are to succeed as a species on the planet.

Historically, girls have not been encouraged to be scientists, to be explorers, and there's a social kind of constraint, of course. Having the responsibility, a disproportionate part of the responsibility, for caring for families, caring for children. I know this challenge from firsthand experience because I have three children and four grandsons.And some of the time I have spent as a scientist and as an explorer has meant choosing to not be with my children and grandchildren as much as I might otherwise have done had I not been a scientist, an explorer.

Success underwater depends mostly on how you conduct yourself. Diving can be the most relaxing experience in the world. Your weight seems to disappear. Space travel will be available only to a few individuals for some time, but the oceans are available to almost everyone - now.